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Should We Crush Gas-Guzzlers? Or Convert Them to Plug In? An Analysis
Oct 3, 2008 (From the CalCars-News archive)
This posting originally appeared at CalCars-News, our newsletter of breaking CalCars and plug-in hybrid news. View the original posting here.
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Introduction by Felix Kramer, CalCars Founder Analysis by Ron Gremban, CalCars Technical Lead

CalCars and Andy Grove have been proposing a major focus on converting "PSVs" (large internal combustion engine gas guzzling Pickups, SUVs and Vans) so they run partially on electricity.­ice-conversions.html. Here we address some of the key non-economic issues in doing so. This analysis starts off pretty simply, and gets to some important numbers in the summary. If you get the first half, don't worry if you decide to skip the technical details in the second half.

Many people agree it's a good idea but are not sure it's practical. They ask questions including, "Can there be a business case? Is it realistic to imagine converting millions of vehicles in less than five years? Can the retrofit infrastructure and component supply chain (batteries/motors) scale up rapidly enough?" Part of the answer to these questions involves whether we are operating with the same urgency and can muster the national will we had in 1943, when we stopped building cars and trucks to tanks and planes -- and after auto industry leaders told FDR they couldn't build 30,000 planes in one year, they built 120,000.

Many people also say -- and we fully agree -- that it's important to get incentives and disincentives right. And we need new advertising messages, and short-term rental deals, so these large vehicles are purchased and used by people who really need them -- not by those who own a big vehicle they use only occasionally to tow a boat, fill with gear, or go off-road.

When we explain that today's PSVs stay on the road for several decades (10-15 years in US, another 10-20 when resold internationally) we often hear the suggestion, from those who see plug-in cars coming within the next five years, "why not just crush the gas-guzzlers and replace them with new large efficient PHEVs?"

Many states have "cash for clunkers" programs, but they are limited in scope. Significant expansion of these programs will have unintended consequences in distorting the resale market, nationally and internationally (as thoughtfully discussed at Freakonomics:­2008/­08/­08/­no-cash-for-clunkers/­.) Of course, we do want carmakers to mass-produce new PHEV PSVs. But many of the same scaling issues apply: can carmakers build enough of them fast enough to reduce petroleum use and thereby improve our prospects on energy security and climate change? That brings us back to our original idea: quickly start to retrofit the fleet, starting with many of the 80 million PSVs in the U.S.

Even if it were possible to crush and replace many of these cars, there is one important underlying question that we haven't been able to answer until now. We haven't known how much energy it takes to build a car, and how much you're thereby throwing away when you crush an old car that operates perfectly well and could be converted into a PHEV PSV.

Now CalCars' Technology Lead Ron Gremban has investigated that question and come up with some answers. We hope you will help distribute this message widely, and that some of you will continue the effort we've begun in developing this model, including the spreadsheet mentioned below that's available at­calcars-crush-or-convert-icevehicles-080930.xls. You can comment on this article at EVWorld's article,­article.cfm?storyid=1540 (if you're a subscriber you'll see it all on one page).

NOTE: This document does NOT address economic costs and payback -- only energy and CO2, which are entirely independent of economic incentives and other policy or business issues!


If you replace your current large or small internal combustion engine (ICE) vehicle with a new PHEV of the same size, it will take over 40,000 miles of driving the PHEV in place of the old vehicle to save as much energy and CO2 emissions as was consumed in the manufacture of the new vehicle! If instead you convert your existing vehicle into a PHEV, you will need to drive only 8,600 miles before beginning to save more energy and CO2 emissions than caused by the conversion process.

This is because it requires as much energy as is contained in 1,822 gallons of gasoline* to manufacture a new mid-sized PHEV PSV (Pickup truck, SUV, or Van), but only the equivalent of 360 gallons -- 1/5 as much -- to convert an existing PSV into a PHEV. For a Prius-sized passenger car, the numbers are 1,035 and 196 gallons respectively.
* burned at 100% efficiency, not the 12-15% efficiency of ordinary ICE vehicles

If you consider only oil consumption, rather than total energy use and CO2 emissions, the savings begin significantly sooner. It's almost immediate for conversions: after 8,000 miles for a new PHEV and only 1,600 miles for a conversion. Here are two hypothetical scenarios (neither of which we're proposing):

If all 248 million light vehicles on the road in the U.S. today were crushed and replaced with PHEVs, the manufacture of the new vehicles would require the energy equivalent of 354 billion gallons of gasoline, or 2.5 years of the total U.S. consumption of 142 billion gallons/year.

Conversion of all 248 million into PHEVs, however, would require only the equivalent of half a year's consumption. So, even if done as quickly as possible, at any time the energy to manufacture conversions will be far more than offset by the savings produced from the conversions already on the road. We think these numbers prove that on a societal basis, converting millions of ICE PSVs is a winning energy-saving strategy. And though we don't address cost issues in this analysis, clearly, if we can reduce the costs of conversions with higher volumes, offset much of the higher first costs by making these conversions eligible for comparable levels of federal incentives as new PHEVs, and offer financing options, the economics will work out too.


For three important environmental factors -- energy consumption, oil consumption, and CO2 emissions -- the question has been raised about how long it takes for the savings after building a new vehicle or converting one into a plug-in hybrid (PHEV) to make up for the cost of manufacture or conversion.

Pablo Paster in a Q&A answer forum­mwt/­feature/­2008/­04/­21/­ask_pablo_cars/­ used data the Argonne National Labs produced, partially by using their GREET model­software/­GREET/­, to come up with such a result for replacing a high-consumption car with a hybrid. He said, in part:

"The Argonne National Lab, a U.S. Department of Energy research center, has analyzed the material intensity and energy consumption of manufacturing vehicles and vehicle fuels. Their work is packaged in GREET models (for greenhouse gases, regulated emissions and energy use in transportation). According to the models, the average conventional internal combustion engine vehicle is made up of 61.7 percent steel, 11.1 percent iron, 6.9 percent aluminum, 1.9 percent copper/brass, 2.9 percent glass, and around 13.6 percent plastic/rubber. This information helps determine the energy required to produce a vehicle.

"The energy required can be measured in British thermal units. A Btu is the amount of energy needed to raise the temperature of a pound of water by one degree Fahrenheit. According to the GREET model, it takes 100.391 million Btus to make the vehicle, batteries and fluids in an average 3,201-pound vehicle. This comes out to 31,362 Btus per pound. The obvious lesson is that, in general, heavier vehicles require more energy to make than lighter vehicles.

"It's been said that hybrids are more environmentally damaging than large SUVs because of the battery production, but this has been widely disputed. According to GREET, a hybrid electric vehicle (HEV) that weighs 2,632 pounds requires 101.726 million Btus to make, or 38,650 Btus per pound (compared to 31,362 for a conventional vehicle). As we will see, this small difference in production energy becomes negligible when you factor in the increased fuel efficiency."

Paster goes on to compare an old Mercedes-Benz, a Hummer H2, and a Prius." See his article at­mwt/­feature/­2008/­04/­21/­ask_pablo_cars/­ for more.

I compiled the following table using that same Argonne National Labs data on the energy to manufacture of a conventional ICE car and a hybrid, information from existing Prius conversions, and some (I believe reasonable) assumptions. Those assumptions, along with my calculations and many more conclusions such as total lifetime energy, oil, and CO2 for various sizes of vehicles and types of propulsion, are detailed in my spreadsheet available at­calcars-crush-or-convert-icevehicles-080930.xls.

I converted the energy costs from BTU into kWh and made two major assumptions that were required due to a lack of further information:

  • CO2 emissions are roughly proportional to the energy content of the fuel and the energy expenditure for manufacture. In the absence of better data, this appears to be a reasonable assumption, as, at 8.9 kg-CO2/gallon and 36.4 kWh/gallon energy content, gasoline combustion releases 245 g/kWh of energy content (only 12-15% of that energy gets to the wheels of an ICE vehicle), just over the 2004 California average of 236 g/kWh for grid electricity. Manufacturing typically uses some coal (high CO2), electricity, oil, and natural gas (low CO2).
  • Oil consumption accounts for 25% of the energy used to manufacture a vehicle. This is an arbitrary number that seems reasonable given that oil's contribution is mainly twofold: as a raw material for plastics and for transportation of parts and completed vehicles. If this assumption is off, it affects only the "...oil consumed..." data in my spreadsheet.

The table below, extracted from my spreadsheet, shows the projected miles one must drive in a new or converted vehicle vs. a higher-consumption vehicle, in order to begin saving more energy or CO2 emissions beyond that caused by the manufacture or conversion of the vehicle. (The results are, of course, not accurate to 4-5 decimal places, but the text quotes the exact numbers in the table's cells to help the reader identify the specific cells.) I looked at two types of PHEVs:

  • FULL EV: capable, like the Chevy Volt, of 40 miles of pure electric driving before using the ICE. Various studies indicate an average of 80% electric propulsion for such vehicles.
  • BLENDED (shown only for the Prius conversion below): limited to blended (electric and ICE) operation, and with only 20 miles of equivalent electric range. I assumed an average of 40% electric propulsion for such vehicles.

Miles a resulting vehicle must be driven to save enough energy and CO2 emissions to make up for what's used in converting the original or manufacturing a new vehicle:

ORIGINAL VEHICLE: A MID-SIZED ICE (internal combustion engine) PSV
(Pickup truck, SUV, or Van)
Miles Resulting vehicle
8,599 PHEV conversion from an existing ICE
19,700 New Prius-sized PHEV (crush the old ICE PSV)
42,200 New mid-sized PSV PHEV (crush the old ICE PSV)

ORIGINAL VEHICLE: A PRIUS-SIZED ICE PASSENGER CAR or hybrid Miles Resulting vehicle 8,617 PHEV conversion from an existing ICE 10,867 PHEV conversion from an existing Prius 44,261 New Prius-sized PHEV (crush the old Prius-sized ICE)

These benefits will accrue starting with the first vehicle built, while the cost benefits will improve with volume, optimized design and declining battery costs.

We repeat the conclusion we reached before the "details" section above: We think these numbers prove that on a societal basis, compared to crushing old vehicles, converting millions of ICE PSVs is a winning energy-saving strategy. And though we don't address cost issues in this analysis, clearly, if we can reduce the costs of conversions with higher volumes, offset much of the higher first costs by making these conversions eligible for comparable levels of federal incentives as new PHEVs, and offer financing options, the economics will work out too.

You can comment on this article at EVWorld's article,­article.cfm?storyid=1540

Ron Gremban, Technical Lead, California Cars Initiative, a nonprofit organization, Newsletter:­news-archive.html
Moderator, PRIUS+ PHEV Conversion Group,

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